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(11)

EP 0 956 381 A1

(12)

(43) Date of publication: 17.11.1999 Bulletin 1999/46 (21) Application number: 97904246.0 (22) Date of filing: 31.01.1997

(51) International Patent Classification (IPC):  C30B 29/ 36( . ) C30B 23/ 00( . ) (86) International application number: PCT/US1997/001864 (87) International publication number: WO 1998/033961 (06.08.1998 Gazette 1998/31)

(84) Designated Contracting States: AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE (71) Applicant: NORTHROP GRUMMAN CORPORATION Los Angeles, California 90067-2199 (US)	(72) Inventors: BARRETT, Donovan, L. Pittsburgh, PA 15235 (US) SEIDENSTICKER, Raymond, G. Pittsburgh, PA 15221 (US) HOPKINS, Richard, H. Export, PA 15632 (US) (74) Representative: O'Reilly, Peter Andrew  Albihns GmbH, Grasserstrasse 10 80339 München 80339 München (DE)